Hundreds of news articles have been written extolling the power of Lloyd’s QML algorithm and the brilliance of its inventor. And now, an 18 year old girl named Ewin Tang has shown (see https://arxiv.org/abs/1811.00414 , https://arxiv.org/abs/1811.04852 , https://arxiv.org/abs/1811.04909 ) that Lloyd’s algo is junk. By the technical term “junk”, I mean that Tang proposed a classical algorithm that does the same thing and is almost as efficient as the quantum one ( i.e., both have very similar time complexity) plus the classical one doesn’t require a quantum computer with QRAM whereas HHL does. (QRAM is a mythological resource that will be much harder to achieve than fault tolerant quantum computing, which itself is a distant dream.)

Before showing that Seth Lloyd’s QML algo is junk, Tang also showed (see https://arxiv.org/abs/1807.04271) that Kerenidis’s quantum algo for recommendation systems is also junk (same def of the word junk as before).

If you think that Ewin Tang might be wrong, think again. Her emperor deflation algorithms have been vetted by respected members of the theoretical computer science community, including Tang’s teacher and advisor for this project, Prof. Scott Aaronson, a famous figure in quantum computing.

Out, out, brief candle!
Life’s but a walking shadow, a poor player
That struts and frets his hour upon the stage
And then is heard no more: it is a tale
Told by an idiot, full of sound and fury,
Signifying nothing.